Our research is concerned with the biosynthesis of oncornavirus proteins and how translational and post-translational events act to control viral multiplication. We are currently investigating several aspects of viral protein biosynthesis: (1) Viral gene expression in normal uninfected tissues: We are involved in the identification and characterization of a series of viral-related polyproteins synthesized by normal chicken embryo tissues. Some of these proteins may be tissue-specific and contain cellular and viral amino acid sequences. (2) Recombinant avian oncornaviruses: We are involved in characterization of altered structural proteins synthesized from regions of the viral genome which are likely to have been involved in recombinational events. We are also examining spontaneously released viruses which also appear to be recombinants. (3) Synthesis of reverse transcriptase: We are identifying polypeptides containing polymerase antigenic determinants from wild-type and mutant viruses in order to define the structure and the cleavage pathway for reverse transcriptase.